TOWN OF PORTER—A town of Porter man admitted he was with a Dane County teen when she died and told authorities they would find her remains in his fire pit, but he denied killing the woman, Sheriff Robert Spoden said Monday.

Nathan C. Middleton, the 29-year-old whose home near Evansville that has been the focus of a sheriff's office investigation since Friday, remained a person of interest in the case, Spoden said.

Authorities have not yet filed criminal charges against Middleton but he remains in custody at the Rock County Jail on suspicion of probation violation, officials said.

Given what Middleton told them, Spoden said authorities believe the remains they found in the home's fire pit are those of a Fitchburg 18-year-old last seen Oct. 27.

“We are confident that this is Aprina Paul,” he said.

Paul had been staying with relatives in Fitchburg, though her permanent home was in Madison, Fitchburg police Lt. Todd Stetzer said.

She was last seen leaving a home in Fitchburg the night of Oct. 27, authorities said. Middleton told police he was with Paul that night, Spoden said, though investigators are working to confirm that.

Middleton and Paul met through a website, Spoden said, though he declined to get any more specific. Stetzer said his department is not releasing information about how Paul and Middleton knew one another.

Middleton told detectives from Fitchburg and the sheriff's office that Paul died inside his home in the 12000 block of West Highway 14 sometime late Oct. 27 or early the morning of Oct. 28 while he was there, Spoden said.

“We have no reason to believe that is not the case,” Spoden said.

Middleton also told detectives he did not kill Paul, Spoden said, and gave an explanation for how she died.

That aspect of the story is still being investigated, as authorities try to determine if Paul's death was from homicide or other causes, Spoden said.

When Fitchburg police interviewed Middleton on Friday, he told them Paul's body was in his fire pit, Spoden said, which launched the sheriff's office investigation.

Along with the remains, authorities found what appear to be clothes and items from a purse that had also been burned in a barrel in Middleton's yard, Spoden said.

An intensive weekend search of the property also turned up computer equipment and other physical evidence inside the house, he said, though he declined to elaborate.

Bones and bone fragments recovered from the fire pit will be examined this week, Rock County Coroner Jenifer Keach said.

Investigators still want to confirm Paul is the person they found, Keach said, and are hoping they'll have enough evidence to determine a cause of death. Along with DNA testing, the office also is looking into dental records and other ways to identify the remains, she said.

“We're working on different angles to get her positively identified,” Keach said.

Authorities could also send some of the remains to a Chicago-area lab that specializes in examining “burnt bone fragments,” Spoden said.

Now, though, Rock County detectives are hoping to retrace Paul's steps before she went missing more than a week ago, Spoden said, to figure out how she might have died.

“Processing that scene and that house and that shed … in itself was very time-consuming,” Spoden said. “This is where we actually start to get into the nuts and bolts of the case.”